"Project Hail Mary" by Andy Weir

A man wakes in some kind of medical room, hooked up to tubes, not remembering his name. 2 long-dead bodies are beside him. Robots ask him simple questions. He's almost paralysed (recovering from induced coma) but he can gradually move, detaching himself from the equipment. He learns about himself (what his accent is, his skills, etc). He recalls the discovery of an Infra Red disturbance - a line from Venus to the Sun. The narrative alternates between 2 timelines - 1) when he started working on the project to deal with the disturbance; 2) when he woke on the ship. In both, he's learning as he goes along, so the infodumping is natural.

Memories return. He's Dr Ryland Grace. It was discovered that the sun was growing dimmer as fast as the disturbance was growing. Before he left academia to become a teacher he had speculated on non-water-based extraterrestrial life. A probe was sent to the line, returning with samples of dust from the line that jiggled - life? He was seconded onto a project to investigate. Knowing that the mission would take years, and that Earth is quickly cooling, artificial global warming is accelerated. He calls the (living?) particles astrophages. He learns in timeline 1 that they stay at 96C and produce energy. He's the first to get them to reproduce. A lab explosion kills some of the project crew, so Grace has to go instead. He resists so he has to be drugged and put on the ship.

In timeline 2 he's on a space ship accelerating fast. His 2 ex crew members were Chinese and Russian. He learns that astrophages fuel the ship he's on. He's by a star called Tau. It's taken 13 years to get there. His mission is to discover why Tau isn't being destroyed though astrophages are present there. It's a suicide mission. There are 4 little ships named after the Beatles which he's supposed to send back to Earth with information.

A space ship (fueled by astrophages) approaches his, and drifts a package his way. He opens it and deduces that the beings come from another star that's been attacked by the astrophages. They make contact, trying to communicate. The being is spider-like - 5 limbs each with 3 fingers. Its atmosphere has lots of ammonia, and it's used to hot temperatures (200C or so). It can't see, but is sensitive to vibrations. It can live 600 years. The being is the only one of the crew to survive. Grace calls it Rocky (he's mineral-based with blood that's largely mercury). Their technology is not as advanced as Earth's - no computers (though they're great calculators). They're unaware of Relativity. They launched a ship to Tau for the same reason that Earth did

Rocky moves into Grace's ship. They enjoy solving problems together. They work out that one of the planets is the astrophages' home planet which has astrophages' natural enemies - "taumoeba". The ship  is damaged when they try to collect samples of taumoeba. Rocky is nearly killed trying to save Grace. They breed a version of taumoeba which they can take back to their people. They part, returning to their respective planets. On the journey back Grace discovers that the taumoeba variant can get through the material that Rocky was storing his samples in, so it will be able to eat his fuel.

He decides to send the taumoeba sample back to Earth on the Beatles and u-turn to save Rocky. He will run out of food. He realises that he could eat taumoeba. He stays on Rocky's planet 16 years. They create food for him, benefitting from his advanced science. He learns that Sol has recovered. He's a teacher.

Other reviews

• thequilltolive (Ryland Grace. Is he just Mark Watney (the protagonist from The Martian) as a school teacher? Sort of, but I think that shrugs off the lack of character behind this one man show. ... The flashbacks following Grace’s journey to the Hail Mary (the ship) were in theory, a great chance to hone and define who Grace was prior to the amnesia. ... The tone of the book was a weird juggling act. Grace’s quippy narration clashed with the moments of profound despair. ... The ending comes across as a total cop out, not because of saving the day, but it rewards Grace’s cowardice and detachment from humanity.)
• twaddle.blog (The realistic science is definitely the strongest point in this book. ... I really enjoyed the plot of this book. ... The biggest issue I had with Project Hail Mary is the lazy national and racial stereotypes. Russians are always drunk or drinking, the Southern US black man calls everyone by their title (even the woman he is sleeping with), the Chinese astronaut is overly formal and polite, and of course the American protagonist/hero is the only person with any real character and depth. )